Chemical mechanical polish pad conditioning device

ABSTRACT

A chemical mechanical polish pad conditioning device is disclosed. The device includes a conditioning substrate made of stainless steel forming a predetermined pattern on a surface. Also, a method of producing a chemical mechanical polish pad conditioning device is disclosed. The method includes providing a conditioning substrate made of stainless steel forming a predetermined pattern on a surface, and applying a hardening process to the surface of the conditioning substrate. The invention further discloses a method of conditioning a chemical mechanical polish pad. The method includes providing a conditioning substrate forming a predetermined pattern on a surface, fixing the conditioning substrate to a conditioning arm, and contacting the surface of the conditioning substrate with a polish pad and moving the conditioning substrate on the polish pad with a predetermined downforce at a predetermined rate of speed. Because the conditioning substrate does not use a diamond layer bonded to the substrate, there is no risk that detached diamonds may become embedded in the polish pad in the course of polishing. Under the configurations of the conditioning device, production of a custom conditioning device that meets specified cut-rate or surface roughness specifications can be achieved

BACKGROUND OF THE INVENTION

[0001] Chemical Mechanical Planarization (CMP) is a technology used in semiconductor wafer fabrication to achieve sub-micron features. CMP is used to planarize the surface of a wafer after a deposition process has been performed. FIG. 1 shows a side view of a conventional wafer polishing apparatus (2). In FIG. 1, a semiconductor wafer (10) is secured to a carrier (12). In order to polish or planarize the wafer (10), the surface of the wafer (10) adjacent to pad (14) is forced downward by carrier (12) against the top surface of the pad (14). Both wafer (10) and pad (14) with attached table (16) are rotated with respect to each other to planarize the surface of the wafer (10). A slurry is deposited or pumped on the pad (14) through pipe (18) to aid in the polishing of wafer (10).

[0002] One of the most critical steps in the CMP process is conditioning of the polish pad surface. Most pads in use today are manufactured from a thermoset plastic such as polyurethane. The pad must be conditioned to get rid of the process affluents and to maintain a precise profile so that planarization occurs in the desired window. Without conditioning, the pad would clog up with process affluents and the profile would change due to the downforce used in the CMP process. Some manufactures use in-situ conditioning, while others use a serial conditioning process. In either case, the conditioning cycle must occur.

[0003] A diamond-coated substrate is a popular choice among current CMP conditioning elements. The diamond-coated device is affixed to a conditioning arm or fixture and moved across the polish pad at a predetermined rate of speed and downforce. This allows the user to control the profile of the pad and to remove a minute portion of the surface thus eliminating the affluents from the previous process cycle. However, in some cases, the torque created by this conditioning process causes diamonds to be pulled from their glue layer and become embedded in the polish pad. During the next planarization cycle, the embedded diamond may scratch the wafer causing the wafer to be irreparably damaged.

SUMMARY OF THE INVENTION

[0004] In general, in one aspect, the present invention relates to a chemical mechanical polish pad conditioning device which comprises a conditioning substrate made of stainless steel forming a predetermined pattern on a surface thereof.

[0005] In general, in one aspect, the present invention relates to a method of producing a chemical mechanical polish pad conditioning device which comprises providing a conditioning substrate made of stainless steel forming a predetermined pattern on a surface thereof, and applying a hardening process to the surface of the conditioning substrate.

[0006] In general, in one aspect, the present invention relates to a method of conditioning a chemical mechanical polish pad which comprises providing a conditioning substrate forming a predetermined pattern on a surface thereof, fixing the conditioning substrate to a conditioning arm, and contacting the surface of the conditioning substrate with a polish pad and moving the conditioning substrate on the polish pad with a predetermined downforce at a predetermined rate of speed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007]FIG. 1 is a side view of an example of a wafer being polished with a polishing pad in accordance with the prior art.

[0008]FIG. 2 is a perspective view of an embodiment of the present invention.

[0009]FIG. 3 is a plan view of a patterned conditioning substrate in accordance with an embodiment of the present invention.

[0010]FIG. 4 is a plan view of a patterned conditioning substrate in accordance with an embodiment of the present invention.

[0011]FIG. 5 is a plan view of a patterned conditioning substrate in accordance with an embodiment of the present invention.

[0012]FIG. 6A is an expanded plan view of pyramid shaped patterns formed on a portion of a conditioning substrate in accordance with an embodiment of the present invention.

[0013]FIG. 6B is a cross sectional view of the pyramid shaped patterns shown in FIG. 6A cut by the line I-I thereof.

[0014]FIG. 7 is a plan view of a template of the patterned conditioning substrate, which is used to form patterns on the surface of the substrate in accordance with an embodiment of the present invention.

[0015]FIG. 8 is a sectional view of the conditioning device in accordance with an embodiment of the present invention.

[0016]FIG. 9 is a table showing a comparison of cut-rate of a conditioning device of an embodiment of the present invention versus a diamond coated conditioning device.

DETAILED DESCRIPTION

[0017] The present invention relates to a conditioning device for a CMP polishing pad which can achieve a precise profile of the CMP polishing pad without using abrasive particles, such as diamonds. The present invention addresses production of custom-patterned conditioning substrates in accordance with desired cut-rate or surface roughness specifications. Referring to the drawings, wherein like elements are described by like reference numbers throughout, embodiments of the present invention are explained as follows.

[0018]FIG. 2 shows a perspective view of an embodiment of the present invention. A holder mechanism (28) includes a conditioning arm (29) and base (26). A bottom surface of the base (26) is provided with a plurality of grooves (27) which are used to flow adhesives therein. The conditioning substrate (24) is made of metal having sufficient hardness, such as stainless steel. A plurality of diamond patterns (30) are formed on the bottom surface of the conditioning substrate (24). When used to condition the polishing pad, the conditioning substrate (24) is attached to the bottom face of the base (26) and the patterned bottom surface of the conditioning device (4) is contacted with the polish pad. It is also possible that the conditioning substrate (24) be fixed to the conditioning arm (29) by using two-sided tape or a magnet without using the base (26).

[0019] FIGS. 3-6 show alternate patterns and shapes of the conditioning substrate (24). These patterns act as abrasive elements while in contact with the polish pad. FIG. 3 shows a diamond pattern formed on the surface of the conditioning substrate (24) in a radial manner from a central point. FIG. 4 shows a diamond pattern formed on the conditioning substrate (24) in a similar but more densely distributed manner. FIG. 5 shows a ring-shaped conditioning substrate (24) with diamond patterns thereon. The patterns are formed on the bottom surface of the conditioning substrate (24) by using chemical etching process. A desired pattern can be created using a CAD drawing of the pattern, which is then used to create the etched template (36) as shown in FIG. 7. By doing this, it is possible to precisely control the pattern and therefore control the amount of polish pad removed for a given time and downforce. These patterns can also be formed by using casting, forging, or machining processes. However, the chemical etching process is generally preferred because it can offer more time and cost-effective production than forging or machining.

[0020] With respect to the design of the patterns, circular, triangular, spiral, or pyramid pattern may also be employed other than the diamond pattern. FIG. 6A shows a partially expanded plan view of the pyramid shaped pattern formed on a conditioning substrate. FIG. 6B shows a cross sectional view of the same cut by the line I-I of FIG. 6A. This pyramid pattern can be effectively formed using a machining process. Although any of these patterns can be used for producing the conditioning substrate, the diamond pattern is generally preferred because it can allow more latitude in adjusting the removal rates than other patterns.

[0021] Once formed, the patterned surface of the conditioning substrate (24) is treated to increase the hardness of the substrate by a hardening process, for example, an ion-nitride treatment process. Using the ion-nitride treatment process, the hardness of the surface of the conditioning substrate (24) can be increased by approximately 20 points of Rockwell hardness. Because the ion-nitride process does not apply extremely high temperature to the substrate, the flatness of the substrate can be maintained at about 12.5 m. A common method used for hardening stainless steel is to heat treat a steel component to a desired temperature and then gradually cool the piece down. However, such high heat treatment may cause the substrate be warped and, as a result, the flatness of the conditioning substrate in relation to the polishing pad would be deteriorated.

[0022]FIG. 8 shows a sectional view of a conditioning device (4) of an embodiment of the present invention. The conditioning substrate (24) is adhered to the bottom of the base (26) at the grooves (27), which are filled with adhesives, such as chemically resistant two-part epoxy. Because the adhesive used for adhering the conditioning substrate (24) flows evenly in the grooves (27), the conditioning substrate (24) can be adhered to the bottom of the base (26) in a highly flat manner in relation to the base (26). It is, of course, possible to attach the conditioning substrate (24) to the base (26) by using other mechanical means, such as screws. However, because of the strict flatness requirement between the conditioning substrate (24) and the base (26), such means significantly increase the complexity of joining the two parts.

[0023] The base (26) with attached conditioning substrate (24) is secured by the holding mechanism (28), which includes conditioning arm (29). Under this configuration, the chemical mechanical polish pad conditioning device (4) is contacted with the surface of the polish pad by a downforce transmitted through the conditioning arm (29) and rotated exactly horizontally on the polish pad with a predetermined downforce and at a predetermined rate of speed. By this operation, the conditioning device (4) can effectively eliminate the process affluents from the previous cycle at a high cit-rate.

[0024]FIG. 9 shows a comparative table wherein cut-rate performance of the conditioning device of an embodiment of the present invention and an electroplated diamond coated conditioning device are compared.

[0025] For comparing the cut-rate performance, a stainless steel conditioning substrate ring having 25.40 cm outside diameter and 20.32 cm inside diameter and an industry standard electroplated diamond conditioning ring having the same outside and inside diameter were prepared. The stainless steel substrate ring was provided with diamond patterns on its bottom surface by using a ferric chloride etching process. The substrate was then treated with an ion-nitride hardening process to obtain a hardness of RC 40. The stainless steel conditioning substrate and the electroplated diamond conditioning device were respectively fixed to a base element which is connected a lapping machine to conduct this test. The test was performed using an IC 1000 pad on a Lapmaster lapping machine. The cut-rate was obtained by measuring the pad before and after the conditioning by the conditioning substrates. All tests were performed using 67 static pounds of downforce on the rings. Each test cycle was 15 minutes. For charting purposes, the average cut-rate over a three-hour interval was plotted.

[0026] Initial cut-rate data was obtained using the diamond-conditioning ring. The stainless steel patterned conditioning substrate ring was then employed with cut-rate data recorded in 15 minute intervals for forty-five hours. The diamond-conditioning ring was then run following the stainless steel ring substrate test.

[0027] As can be seen from the table, the results of the test indicates that the removal rate attained by the stainless steel patterned conditioning substrate is comparable to that which has been achieved by the diamond conditioning device.

[0028] Advantages of the present invention may include one or more of the following. In one or more embodiments, because the conditioning substrate does not use a diamond layer bonded to the conditioning substrate, there is no risk that detached diamonds may become embedded in the polish pad in the course of polishing. Because the surface of the conditioning substrate is kept extremely flat in relation to the polishing pad, a precise profile of the polish pad can be achieved by using the conditioning device of an embodiment of the present invention. Also, because the etching pattern can be created on an etch template using CAD system, it is possible to precisely control the pattern and therefore control the amount of polish pad removed for a given time and downforce. Because the conditioning substrate can be adhered to the base in a very flat manner, the conditioning substrate can be maintained flat in relation to the polishing pad. As a result, even polishing of the pad can be achieved. Given the configurations of the conditioning device described above, production of a custom conditioning device that meets specified cut-rate or surface roughness specifications can be achieved.

[0029] While the present invention has been described with respect to a limited number of preferred embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. The appended claims are intended to cover all such modifications and variations which occur to one of ordinary skill in the art. 

What is claimed is:
 1. A chemical mechanical polish pad conditioning device, comprising: a stainless steel conditioning substrate having a predetermined pattern formed on a surface thereof.
 2. The device according to claim 1, further comprising: a base; wherein the conditioning substrate is fixed in flat relation to the base.
 3. The device according to claim 2, wherein a surface of the base is provided with a plurality of grooves and the conditioning substrate is adhered to the base by an adhesive placed in the grooves.
 4. The device according to claim 1, wherein a hardening process is applied to the surface of the conditioning substrate.
 5. The device according to claim 4, wherein the hardening process is an ion-nitride treatment process.
 6. The device according to claim 1, wherein the pattern on the surface of the conditioning substrate is formed by a chemical etching process.
 7. The device according to claim 1, wherein the pattern on the surface of the conditioning substrate is formed by a casting process.
 8. The device according to claim 1, wherein the pattern on the surface of the conditioning substrate is formed by a forging process.
 9. The device according to claim 1, wherein the pattern on the surface of the conditioning substrate is formed by machining.
 10. The device according to claim 1, wherein the pattern on the surface of the conditioning substrate is formed in a diamond shape.
 11. The device according to claim 1, wherein the pattern on the surface of the conditioning substrate is formed in a circular shape.
 12. The device according to claim 1, wherein the pattern on the surface of the conditioning substrate is formed in a triangular shape.
 13. The device according to claim 1, wherein the pattern on the surface of the conditioning substrate is formed in a spiral shape.
 14. The device according to claim 9, wherein the pattern on the surface of the conditioning substrate is formed in a pyramid shape.
 15. A method of producing a chemical mechanical polish pad conditioning device, comprising: forming a predetermined pattern on a stainless steel conditioning substrate. applying a hardening process to the surface of the conditioning substrate.
 16. The method according to claim 15, further comprising fixing the conditioning in flat relation to a base.
 17. The method according to claim 16, disposing a plurality of grooves in a surface of the base; and adhering the conditioning substrate to the base by an adhesive placed in the grooves.
 18. The method according to claim 15, wherein the hardening process is an ion-nitride treatment process.
 19. The method according to claim 15, further comprising: the pattern on the surface of the conditioning substrate by a chemical etching process.
 20. The method according to claim 15, further comprising: the pattern on the surface of the conditioning substrate by a casting process.
 21. The method according to claim 15, wherein the pattern on the surface of the conditioning substrate is formed by using a forging process.
 22. The method according to claim 15, further comprising: forming the pattern on the surface of the conditioning substrate by machining.
 23. The method according to claim 15, further comprising: forming the pattern on the surface of the conditioning substrate in a diamond shape.
 24. The method according to claim 15, further comprising: forming the pattern on the surface of the conditioning substrate in a circular shape.
 25. The method according to claim 15, further comprising: forming the pattern on the surface of the conditioning substrate in a triangular shape.
 26. The method according to claim 15, further comprising: forming the pattern on the surface of the conditioning substrate in a spiral shape.
 27. The method according to claim 22, further comprising: forming the pattern on the surface of the conditioning substrate in a pyramid shape.
 28. A method of conditioning a chemical mechanical polish pad, comprising: forming a predetermined pattern on a surface of a conditioning substrate; fixing the conditioning substrate to a conditioning arm; contacting the surface of the conditioning substrate with the polish pad; and moving the conditioning substrate on the polish pad with a predetermined downforce at a predetermined rate of speed.
 29. The method according to claim 28, further comprising: fixing the substrate in flat relation to a base connected to the conditioning arm.
 30. The method according to claim 29, further comprising: providing a plurality of grooves in a surface of the base and adhering the conditioning substrate to the base by an adhesive placed in the grooves.
 31. The method according to claim 28, further comprising: applying a hardening process to the surface of the conditioning substrate.
 32. The method according to claim 31, wherein the hardening process is an ion-nitride treatment process.
 33. The method according to claim 28, further comprising: forming the pattern on the surface of the conditioning substrate by a chemical etching process.
 34. The method according to claim 28, further comprising: forming the pattern on the surface of the conditioning substrate by a casting process.
 35. The method according to claim 28, further comprising: forming the pattern on the surface of the conditioning substrate by a forging process.
 36. The method according to claim 28, further comprising: forming the pattern on the surface of the conditioning substrate by machining.
 37. The method according to claim 28, further comprising: forming the pattern on the surface of the conditioning substrate in a diamond shape.
 38. The method according to claim 28, further comprising: forming the pattern on the surface of the conditioning substrate in a circular shape.
 39. The method according to claim 28, further comprising: forming the pattern on the surface of the conditioning substrate in a triangular shape.
 40. The method according to claim 28, further comprising: forming the pattern on the surface of the conditioning substrate in a spiral shape.
 41. The method according to claim 36, further comprising: forming the pattern on the surface of the conditioning substrate in a pyramid shape. 